Our laboratory is interested in the molecular basis of human cancer. Our approach is to study the normal and malignant functions of genes implicated in human cancer at the level of the cell and the entire organism. In addition, we aim to exploit the differences between tumor and normal cells to identify strategies which selectively kill tumor cells.

1. Mitotic checkpoint genes and oncogenic kinases in normal and neoplastic growth

One of the most striking differences between normal and tumor cells is that normal cells are diploid and chromosomally stable whereas tumor cells are typically aneuploid and exhibit chromosomal instability. A key mechanism which maintains chromosome stability is the mitotic spindle checkpoint, an inhibitory signaling circuit that delays the onset of anaphase until all the chromosomes are stably attached to the microtubule spindle apparatus via their kinetochores. Using human tissue culture cells, transgenic and knock-out mice as model systems, we are dissecting the spindle checkpoint at the molecular level, focusing on the protein kinase components, namely Bub1, BubR1, Mps1 and their novel interacting proteins. In addition, we are developing mouse models to investigate the role of the spindle checkpoint in the wider context. This work will yield new insights into the molecular workings of a checkpoint mechanism that ensures a high fidelity of chromosome segregation, and may be applicable for testing the clinical significance of this analysis in tumor suppression.



2. Chemosensitization and recovering from chemoresistance in response to spindle damage

Aurora kinases and polo-like kinase play a crucial role in cellular division by controlling chromatid segregation, and are aberrantly and highly overexpressed in the variety of human cancer cells. Deregulations of these mitotic kinases cause severe mitotic defects and anueuploidy and/or genetic instability, conditions which are highly associated with tumorigenesis, leading to cell death or disease. Therefore, these kinases could be useful therapeutic targets against human cancers. Recently, we have started to identify the binding substrate proteins in order to rigorously delineate on- and off-target effects, both in cultured cells and in vivo. This study aims to design novel anti-cancer strategies; (A) Screening and functional studies of novel mitotic checkpoint regulatory protein and anti-cancer targets, (B) In vivo cross-talk between the oncogenic mitotic kinases and chemosensitization, (C) In vivo relevances of mitotic kinases in human pathogeneses.


3. Identification of anti-cancer drug response biomarkers through functional genetic screens

Gain-of-function genetic screens. Collections of cDNAs are ectopically expressed in drug-sensitive cells, either in polyclonal format or in an arrayed format in multi-well plates, often through use of a viral vector system (retroviral, lentiviral, or adenoviral). Cells are exposed to a cancer drug and resistant cells will continue to proliferate. From drug-resistant colonies, cDNAs can be recovered, identified by sequence analysis, and re-tested for their ability to confer drug resistance. Short hairpin RNA (shRNA) barcode loss-of-function genetic screens. Collections of shRNA vectors are expressed polyclonally in drug-sensitive cells and subjected to drug selection. Cells harboring an shRNA vector that confers drug resistance will become enriched in the population, shRNAs that enhance the sensitivity to a cancer drug will become depleted under drug selection compared to a reference population that is not exposed to drug




4. Sister chromatid cohesion and its relation to human cancer

Sister chromatid separation in anaphase depends on the removal of cohesin from chromosomes. Several years ago we discovered that this process depends on two mechanisms in vertebrate cells: the dissociation of cohesin from chromosome arms in prophase, and the proteolytic cleavage of cohesin at centromeres in metaphase. The prophase pathway depends on the cohesin-associated protein Wapl, whereas the metaphase pathway is mediated by the protease separase. Although the prophase pathway was identified several years ago, its function and importance for chromosome segregation are still unknown. Our recent genetic screens using the yeast-two hybrid assay identified novel cohesin-binding protein that prevents the removal of cohesion from chromosome arms. Therefore, our research will contribute to a better understanding of human cancer because chromosome abnormality, such as aneuploidy and translocations, is tightly associated with tumor development and birth defects. We are aiming to understand; the physiological significance of novel regulatory genes (SSU72 and CCP1) using transgenic mice and conditional knock-out mice (established), and in vivo significance of polymorphisms, expression and modification of the novel cohesion regulatory protein in human cancer




5. Cell cycle, division and differentiation lineage of human adult stem cells and undifferentiated progenitor cells

1) Our new interest is to understand the molecular analyses of the cell cycle control and cell division of adult stem cell and progenitor cells. The goals of this research field are to establish the tissue culture condition, to understand the molecular mechanisms of cell cycle control, self-renewal, asymetric cell division and differentiation lineage, and to screen the differentiation surface marker proteins of human adult stem cells (ADSCs and BM-MSCs). Therefore, this study may provide substantial evidences to know the molecular mechanisms of proliferation, division and differentiation of adult stem cells, and may be the basis for future clinical applications.

2) In addition, we are also aiming to underly the molecular mechanism of cell division, cell death and differentiation of adult stem cells (ADSCs, BM-MSCs) and undifferentiated progenitor cells (Neural precursor cells, B and T lymphocytes) by mitotic checkpoint proteins and mitotic kinases.



Copyright 2009 Laboratory of Molecular Tumor Biology, Department of Molecular Cell Biology

Sungkyunkwan University School of Medicine, Suwon 440-746, Korea

Phone : +82-31-299-6153 (Lab)  Fax : +82-31-299-6109